Boosting a signal-to-interference ratio of a mobile station

ABSTRACT

Techniques for transmitting encoded data packets to one or more mobile stations in a communication system including a cell that has sectors serving at least partially different geographic areas. The techniques include transmitting in a first sector an encoded data packet in one or more time slots to a mobile station; reducing transmission power in a second sector during one or more of the time slots in which the first sector transmits the data packet to the mobile station; decoding at the mobile station the encoded data packet after each time slot; transmitting by the mobile station a signal indicating acknowledgment of the packet reception when the decoding of the packet is successful; and in response to receiving the acknowledgement signal, ceasing transmission of the data packet in the first sector in subsequent time slots.

This application is a continuation of U.S. patent application Ser. No.09/976,240, filed Oct. 12, 2001, and claims the benefit of priority fromthat application.

BACKGROUND

This invention relates to boosting a signal-to-interference ratio of amobile station.

In our discussion, we use the following acronyms:

MS Mobile Station BS Base Station CDMA Code Division Multiple AccessFDMA Frequency Division Multiple Access TDMA Time Division MultipleAccess SIR Signal to Interference Ratio HARQ Hybrid ARQ ARQ AutomaticRepeat Request GSM Groupe Speciale Mobile of the EuropeanTelecommunication Standards Institute. AMPS Advanced Mobile PhoneService CDMA 2000 Third generation CDMA standard for mobile wirelesscommunication. 1xEV-DO 1x Evolution Data Only standard. 3GPP2 ThirdGeneration Partnership Project 2

In a wireless communication system, limited available resources such asfrequency and time are shared among the users of the system. As shown inFIG. 1, in a cellular system 10, a covered area is divided into cells12, and each cell is served by a base station (BS) 14. To increasecapacity for a given frequency spectrum being used, a BS's service areamay be further divided into sectors 16, for example, three sectors,using directional antennas, as described in T. S. Rappaport, WirelessCommunications. Prentice Hall, 1996. Some cellular systems, such as TDMA(GSM, IS-54) and FDMA (AMPS), use so-called frequency reuse or frequencyplanning to increase communication capacity.

In a frequency reuse system, the same frequency channels are reused inmultiple cells. In FIG. 1, for example, all three cells 12, 13, 15 havesectors 16, 18, 20 that bear a given letter (e.g., the letter “C”)indicating that they use the same frequency channel.

Frequency reuse helps users at cell edges, for example, user 22, locatedat the edge 24 of a cell to achieve a better signal to interferenceratio (SIR).

As more and more carrier frequencies are used for frequency reuse, theSIRs of the users in a given cell get better and the SIR distributionamong users of the cell gets more even. However, the spectral efficiencygets lower, which will result in lower total system capacity for a giventotal spectrum.

CDMA systems such as IS-95A/B, CDMA-2000, and 1×EV-DO incorporatemaximal frequency reuse in which neighboring cells use the same carrierfrequency, i.e., the reuse factor (defined as the number of frequencychannels used)=1. Different codes are used to differentiate differentcells. This system yields good spectral efficiency, but the SIRdistribution within a cell can be uneven depending on the location ofthe user.

The SIR of a user at a given location is determined by the locations andconfigurations (e.g., omni cell or three-sectored cell) of the cells.The SIR in turn determines the instantaneous communication rate of theuser.

Recently, 3GPP2 approved a new wireless packet data air interfacestandard called IS-856, sometimes also referred to as 1×EV-DO. IS-856provides the capability to support high-speed wireless Internetcommunication at speeds up to 2.45 Mbit/s using only 1.25 MHz spectrum.

FIG. 2 shows an example, for 1×EV-DO, of the percentage distribution offorward link rates of users who are uniformly distributed geographicallywithin a three-sectored cell. As can be seen from the figure, the lowestand highest rates, 38.4 kbps and 2.4 Mbps, differ by a factor of 64.This large difference in rate makes it hard to achieve an eventhroughput to all users in a cell, as is required for constant bit-rateapplications such as voice. For data applications, a certain degree ofunfairness, e.g., giving higher throughput for users who are close tothe BS and lower throughput for users who are far from the BS, isallowed as long as it does not violate certain fairness conditions.

Because the forward link of 1×EV-DO is TDMA, it is possible to allocatedifferent amounts of time for each user to increase the fairness, i.e.,by giving more time slots for low SIR users and fewer time slots forhigh SIR users. However, this will lower the throughput of the overallsystem because low SIR users will consume a large share of theresources. Systems designed to increase fairness tend to reduce sectorthroughput.

SUMMARY

In general, in one aspect, the invention features a method that includesin a cell of a cellular wireless communication system, altering the SIRof at least one user in a sector of the cell by temporarily reducingtransmissions on a forward link in at least one other sector of the cellor a sector in another cell in accordance with a pattern.

Implementations of the invention may include one or more of thefollowing features. The pattern is organized in a sequence of timeslots, and the pattern defines which of the sectors has transmissionsturned on or off in each of the time slots. The pattern comprises apredetermined fixed pattern that is repeated as time passes. A currentstate of transmissions is determined in at least one of the sectors ofthe cell or a sector in another cell, and the pattern is set dynamicallybased on the determined state of the transmissions. The current state oftransmissions includes the scheduling status of transmissions inneighboring sectors in the cell or in one or more other sectors in oneor more other cells. Neighboring sectors include other sectors in thecell and sectors in some other cells. The current state of transmissionsincludes the transmission rates of some neighbor sectors. The currentstate of transmissions includes the next time slot usage. The currentstate of transmissions includes the forward link SIR. The current stateof transmissions includes user location. The current state oftransmissions includes a fairness setting. The current state oftransmissions includes an application type of user and/or QoS. Thetransmissions are temporarily reduced by turning transmissions on andoff in selected sectors according to the pattern. The pattern includesturning off transmissions in other sectors more frequently to help usershaving lower communication rates. A frequency reuse factor of one orhigher is used in the wireless system. The wireless system comprises1×EV-DO.

In general, in another aspect, the invention features apparatus thatincludes (a) wireless transmission facilities for more than one sectorof a cell, and (b) control facilities connected to the wirelesstransmission facilities and configured to alter the SIR of at least oneuser in a sector of the cell by temporarily reducing transmissions on aforward link in at least one other sector of the cell or a sector inanother cell in accordance with a pattern. Implementations of theinvention may include one or more of the following features. The controlfacilities comprise sector controllers for controlling the wirelesstransmission facilities for the respective sectors.

In general, in another aspect, the invention features a medium bearingintelligence configured to enable a machine to effect the actions thatcomprise: in a cell of a cellular wireless communication system,altering the SIR of at least one user in a sector of the cell bytemporarily reducing transmissions on a forward link in at least oneother sector of the cell or a sector in another cell in accordance witha pattern.

In general, in another aspect, the invention features apparatus thatincludes a sector controller adapted to control transmissions in asector of a cell of a wireless communication system and to communicatewith other sector controllers in the cell or in one or more other cellsto coordinate the turning on and off of transmissions in at least one ofthe sectors based on the transmission state in at least another one ofthe sectors.

Other advantages and features will become apparent from the followingdescription and from the claims.

DESCRIPTION

FIG. 1 shows frequency or time reuse factor of three.

FIG. 2 shows a bar chart of rate distribution for frequency or timereuse factor of one.

FIG. 3 shows a bar chart of a rate distribution for frequency or timereuse factor of three.

FIG. 4 shows a three-sectored base station

Here, we propose a system in which some BS's turn off theirtransmissions in forward links to boost the SIR of a user in a badlocation and thereby achieve good rates and more even rates among usersin a cell. By employing this technique, the system can achieve a moreconcentrated rate distribution (less variance in the rate) than shown inFIG. 2 and thereby can provide more even throughput to users andincrease the sum of throughput of all users in a sector, i.e., thesector throughput.

This system can be thought of as a time reuse system in which differentsectors use different time slots to boost SIR of users in the respectivesectors. Unlike a frequency reuse system, the time reuse pattern can beeasily adjusted dynamically based on an SIR measurement, the location ofthe user, the application type being run on the user's device, orconfiguration data such as a fairness setting, e.g., a setting thatguarantees a certain limit on the ratio of the maximum and minimum userthroughput or a minimum throughput. Also, the time reuse pattern may bedisabled easily.

Although we shall explain the benefits of time division multiplexingamong sectors in the context of an example that concerns 1×EV-DOsystems, benefits can be achieved in other wireless systems, includingTDMA, CDMA, and OFDM systems.

Let M be the number of sectors in a cell. We assume a frequency reusefactor of one, i.e., every sector in a cell uses the same frequency. Weassume that the same number, K, of active MSs are operating in eachsector. The analysis can be generalized to cover cases in whichdifferent numbers of MSs are operating in respective sectors.

We assume each MS chooses the best serving sector from which to downloaddata, although, in reality, there can be some delay in switchingsectors.

We consider two cases of time reuse: fixed and adaptive. In a fixed timereuse pattern, sectors are turned off at times that are defined by apre-determined pattern. In an adaptive reuse pattern, the timing of theturning off of sectors depends on the status of the system such as thenext time slot usage in each sector. For example, when a low-rate useris using the next time slot in a sector, some neighbor sectors can beturned off during the slot to help the disadvantaged user.

Fixed Reuse Pattern

Let S be a local group of sectors in a cell whose transmission states(on and off) will be controlled jointly. S could be fewer than all ofthe sectors in the cell. Assume that the pattern of on and off states isrepeated in successive control periods, and that each control periodincludes a number L of time slots. Let Si be the set of sectors allowedto transmit in the time slot Ti, where i=1, . . . , L. Such a pattern isillustrated in the following table for the case of four sectors in S andfour time slots. The lengths of time slots Ti's can be different ingeneral.

T1 T2 T3 T4 Sector 1 On Off On Off Sector 2 Off On On Off Sector 3 OnOff Off On Sector 4 Off On Off On

In this example, S={Sectors 1, 2, 3, and 4}, S1={Sectors 1 and 3},S2={Sectors 2 and 4}, S3={Sectors 1 and 2}, and S4={Sectors 3 and 4}.

Another example is shown in FIG. 1, where S contains three sectors in acell, S1={A}, S2={B}, S3={C}, and there are three time slots T1=T2=T3=T.

In FIG. 3, we show the percentage distribution of users by rate for thiscase, representing a clear improvement in the throughput compared to thedistribution of FIG. 2. (Because each of the sectors is active only for⅓ of the time, the throughput needs to be scaled down by a factor of 3.)

We use two quantities to measure performance. We define the equal-timethroughput E[R], where R is the instantaneous rate, per cell per carrieras the expected cell throughput per carrier (the 1.25 MHz band in caseof 1×EV-DO), i.e., the average rate of a user randomly located in thesector. This is the cell throughput per carrier under the condition thatevery user gets the same amount of serving time. We define theequal-data throughput 1/E[1/R] per cell per carrier as the expected cellthroughput per carrier when each user downloads the same amount of dataindependent of its channel condition, which is equal to the inverse ofthe expected value of the inverse of the rate R. These throughput valueswill be scaled down by the reuse factor to include the effect of reducedtime usage due to time reuse.

In the example above (FIG. 1), we get the following simulation resultsassuming 19 hexagonal three-sectored cells:

E[R] 1/E[1/R] FIG. Time reuse = 1 2923 kbps 1520 kbps 2 Time reuse = 32105 kbps 1864 kbps 3 Gain −28% 23%

Although we loose 28% in equal-time throughput, we gain 23% inequal-data throughput when the time reuse=3 is used. Therefore, the timereuse of three in this example improves performance of systems with highfairness among users.

In 1×EV-DO, even when the data portion of a time slot is empty, thepilot portion is transmitted. The MS then determines its DRC (Data RateControl, i.e., the rate at which the MS asks a sector to send data inthe forward link) based on the pilot only. Therefore, even when the dataportions of time slots from interfering sectors are empty, and thereforethe MS could receive at high rate, its DRC will still be low. Eventhough the BS normally would transmit to the sector at the rate (here,the low rate) that the MS has requested, it is still possible to takeadvantage of the boosted channel condition that time reuse provides. Forexample, 1×EV-DO uses HARQ, which permits the MS to send an ACK signalto alert the sector to stop transmission of the remaining slots ofmulti-slot packets and thereby effectively increase the transmissionrate.

Adaptive Reuse Pattern

Forward link capacity can be improved by a time reuse scheme that isadaptive. Let I={I_(i) |i=1, . . . , M-1 represent the set ofinterferences from other sectors, where I_(i) denotes the ratio of theinterference from the i-th sector to the power from the serving sectorfor a user (the serving sector is the sector from which the user isreceiving packets), M>>1 is the total number of sectors. Let N denotethe ratio of the noise to the power in the serving sector. We assumeI_(i) and N are random variables that depend on the user location andshadow fading. To simplify the derivation, we assume no Rayleigh fading(thus no multi-user diversity gain).

Then, channel capacity C is given by

${C = {{\log_{2}\left( {1 + \frac{1}{N + I_{A}}} \right)}\mspace{14mu}\left\lbrack {b\text{/}s\text{/}{Hz}} \right\rbrack}},$where I_(A)=sum(I_(i), i=1, . . . , M-1) is the aggregate interferencefrom other sectors.

Let m=m(I_(A)) be the number of other sectors with largest I_(i)'s to beturned off during transmission for the current user. m is a randomvariable that depends on I_(A) (or equivalently the DRC of the user witha little less accuracy), m could be a function of I_(i)'s in general,but that could make the system too complicated.

Let q(N,I) be the relative serving time for a user characterized by{N,I}, i.e., E[q(N,I)]=1. For example, for Qualcomm's fair proportionalscheduler (Qualcomm, 1xEV Scheduler: Implementation of the ProportionalFair Algorithm, Application Note, 80-85573-1 X5, Jun. 27, 2001), if allqueue's are backlogged, or when each user receives data whose amount isproportional to its supportable rate, then q(NI)=1. If every user hasthe same amount of data to receive, then q(N,I)=1/R(N,I)/E[1/R(N,I)],where R(N,I) is the rate supportable at {N,I}. We simply denote q(N,I)by q and call it the user bandwidth vector. Let α denote

${\frac{E\lbrack q\rbrack}{E\left\lbrack {q\left( {m + 1} \right)} \right\rbrack} = \frac{1}{E\left\lbrack {q\left( {m + 1} \right)} \right\rbrack}},$which is the average fraction of time a sector is turned on during theperiod assuming there is no sector with an empty queue. The channelcapacity C′ of this time reuse scheme becomes:

${C^{\prime} = {\alpha\mspace{11mu}{{\log_{2}\left( {1 + \frac{1}{N + {\beta\left( {I_{A} - I_{m}} \right)}}} \right)}\mspace{14mu}\left\lbrack {b\text{/}s\text{/}{Hz}} \right\rbrack}}},$where I_(m)=sum of m largest I_(i)'s. 0≦β≦1 is the factor that reducesthe interference as a bonus of turning off some sectors. That is,turning off some sectors not only reduces the interference I_(A) byI_(m), but also reduces the interference further because other sectorsare also turned off during the period. Because there is no HARQ for highrate packets, i.e., one-slot packets with rates 1842.3 or 2457.6 kbps,these rates will not usually benefit from the reduced β. This effectwould produce only a minor degradation on R′ when q′ is inverselyproportional to R′. If there is an adaptive DRC estimation algorithmemployed in MSs that can estimate the increased SNR due to some silentsectors, the 1843.2 kbps rate would benefit, i.e., it could become2457.6 kbps sometimes.

If we make the unrealistic assumption that sectors are perfectlycoordinated so that when a sector needs to be turned off in the nexttime slot to boost the SIR of a MS, it does not have any packet to sendin the slot, we get β=α. Because there is some correlation in the timeswhen neighbor sectors are turned off, β would usually be slightly largerthan α. The difference would widen (slightly) if m is large becauseother sectors will have less chance to be turned off in that m sectorsare already turned off and there is no traffic in those m sectors.However, E[β] would be close to α. Therefore, we assume β=α.

Analysis and Simulation Results

Because channel capacity increases only logarithmically at large SNR,and the adaptive reuse technique does not help high rate communications,we arrange to turn off sectors only for users with low rates. Using alow-SNR approximation, we get the achievable rate R, i.e.,

$\begin{matrix}{{R \approx {\lambda\;{\frac{1}{N + I_{A}}\mspace{14mu}\left\lbrack {b\text{/}s\text{/}{Hz}} \right\rbrack}}},} & (1)\end{matrix}$where λ≈0.5 at rates 38.4˜1228.8 Kbps and λ≈0.25 at rates 1843.2˜2457.6Kbps in a 1×EV-DO system. Because we are not attempting any improvementfor high rate users, we can safely assume λ=0.5 for the analysis of thethroughput improvement for low-rate users.

The improved rate R′ becomes

$R^{\prime} \approx {\lambda\;{{\frac{\alpha}{N + {\beta\;\left( {I_{A} - I_{m}} \right)}}\mspace{14mu}\left\lbrack {b\text{/}s\text{/}{Hz}} \right\rbrack}.}}$

This approximation will be accurate if the improved SNR=

$\frac{1}{N + {\beta\left( {I_{A} - I_{m}} \right)}}$is less than about two, i.e., we can still assume λ=0.5. We use

$\alpha = \frac{1}{E\left\lbrack {q^{\prime}\left( {m + 1} \right)} \right\rbrack}$for the adaptive reuse case, since q′ depends on the improved R′ ingeneral.

Based on the user bandwidth vectors q and q′ for the original case (timereuse=1) and the adaptive reuse case, we get the sector throughputsS=E[q R] and S′=E[q′R′] for the original case and the adaptive reusecase, respectively. In the following throughput analysis, we demonstratehow much gain we can get using adaptive reuse.

Case I (Time Reuse=1)

For case I, q=1/R/E[1/R] and q′=1/R′/E[1/R′]

In this case, we assume β=α. S and S′ become

$\begin{matrix}{S \approx {\frac{1}{{E\left\lbrack {N/\lambda} \right\rbrack} + {E\left\lbrack {I_{A}/\lambda} \right\rbrack}}\mspace{14mu}{and}}} \\{S^{\prime} \approx {\frac{1}{{{E\left\lbrack {N/\lambda} \right\rbrack}/\alpha} + {E\left\lbrack {I_{A}/\lambda} \right\rbrack} - {E\left\lbrack {I_{m}/\lambda} \right\rbrack}}.}}\end{matrix}$

If N is sufficiently small (if not coverage limited, i.e., cell sizesare small), then S′ will be always greater than S. Although λ depends onthe rate R and R′ for the original and the adaptive cases, respectively,we simply assume λ is a function of R because we are not attempting toincrease R′ for high rate users and in this case λ is almost constantanyway.

Assuming N=0, we get

$\alpha = {\frac{E\left\lbrack {\left( {I_{A} - I_{m}} \right)/\lambda} \right\rbrack}{E\left\lbrack {\left( {I_{A} - I_{m}} \right){\left( {m + 1} \right)/\lambda}} \right\rbrack}.}$

In this case, the throughput gain g=S′/S becomes

$g = {\frac{E\left\lbrack {I_{A}/\lambda} \right\rbrack}{E\left\lbrack {\left( {I_{A} - I_{m}} \right)/\lambda} \right\rbrack}.}$

We assume hexagonal three-sectored cells, an antenna pattern defined inthe 1×EV-DV evaluation methodology document (3GPP2, 1×EV-DV EvaluationMethodology—Addendum (V5)), and shadow fading of 8.9 dB with basestation correlation of 0.5. We randomly locate 10,000 users uniformlyand find the serving sector and the set of interferences I for eachuser. The following table summarizes the rate R and its occurrence.

Rate [kbps] Fraction of users 38.4 0.0002 76.8 0.0169 153.6 0.0875 307.20.2116 614.4 0.1749 921.6 0.0979 1228.8 0.1898 1843.2 0.0702 2457.60.1510

We choose the distribution of m as a function of R to maximize the gaing given that α≧α₀ for various thresholds α₀. We show results fordifferent values of α₀. Although we get better results by reducing α,making α too small would have undesirable effects such as increasingnoise N by 1/α. We limit m to be less than or equal to 0, 10, 5, and 1for R=38.4, 76.8, 153.6, and 307.2, respectively. We set m=0 for R=38.4kbps because it does not affect the performance much due to its smallprobability of occurrence. For rates >307.2 kbps, we assume m=0. Thefollowing table shows optimized m(R)'s for various thresholds α₀.

α₀ {m(76.8), m(153.6), m(307.2) g-1 α 0.9 {1, 0, 0} 1% 0.93 0.8 {10, 0,0} 7% 0.81 0.7 {2, 0, 1} 17% 0.71 0.6 {1, 1, 1} 24% 0.62 0.5 {0, 5, 1}41% 0.52 0.0 {10, 5, 1} 55% 0.42

For example, the final line of the table indicates that a throughputgain of 55% is possible if the number of sectors that are turned off foreach of the three rates indicated at the top of the table arerespectively 10, 5, and 1. The average time during which sectors areturned off is 58%.

This result shows that turning off as many sectors as possible resultsin the best performance. The adaptive reuse scheme for 38.4 Kbps usersdoes not change the above result much because they do not occur oftenanyway, but increasing m for those users will improve their userexperience.

The following table summarizes how much gain is possible for each ratewhen {10,5,1} is used for the m(R)'s. It shows that the adaptive reusescheme can improve the throughput of low rate users by as much as 352%even after the penalty due to silent periods. The improved rates dividedby α are all within our valid approximation range. However, some usersmay have highly improved rates that are outside our valid approximationrange. Because these numbers already include the penalty that we are notusing all time slots, this throughput gain is the real gain in user'sexperience.

Improved rate Throughput Original rate [kbps] [kbps] gain 76.8 347 352%153.6 513 234% 307.2 500 62%Case II

For case II, q=q′=1

In this case, S and S′ become

$S \approx {{E\left\lbrack \frac{\lambda}{N + I_{A}} \right\rbrack}\mspace{14mu}{and}\mspace{14mu} S^{\prime}} \approx {{E\left\lbrack \frac{\alpha\lambda}{N + {\beta\left( {I_{A} - I_{m}} \right)}} \right\rbrack}.}$

Using the same assumptions as in the first case, we getα=1/E[m+1]and

${g = \frac{E\left\lbrack {{\alpha\lambda}/{\beta\left( {I_{A} - I_{m}} \right)}} \right\rbrack}{E\left\lbrack {\lambda/I_{A}} \right\rbrack}},$where we assume β=α for R<=1.2288 Mbps and β=1 for R>1.2288 Mbps becausehigh rates do not benefit much from silent sectors and this will have amore significant effect on the throughput gain than in the first case.

In this case, the maximum gain g of one is achieved when m is alwayszero for all R. This means the adaptive reuse should not be used forthis traffic model, which is intuitive because all rates are fair inthis case.

EXAMPLES

In this section, we discuss examples of an adaptive time reuse scheme.

As shown in FIG. 4, the sector control arrangements 52 can beimplemented in software, firmware, or hardware running on a base station50. The sector control arrangements include sector controllers(schedulers) 40, 42, 44 that determine which users in a sector will beserved and provide control signals 54 that control the transmissionstate of the sector antennas 56, 58, . . . , 60.

Let Qi(R) be a set of sectors that ought to be turned off when the i-thsector 58 is transmitting to a user with rate R 61. Let R0 denote a setof rates considered as low rates that need to be boosted by turning offsome neighbor sectors. With respect to sector i, the scheduler 42 firstdetermines to which user in the sector to give the next time slot if itis available. If the rate R of the user to whom it will give the timeslot is in the set R0, then the scheduler for that sector requestsneighbor sectors, e.g., sector 56 in Qi(R) not to schedule any packet inthe next slot if possible. The scheduler 42 schedules a packet to theuser 61 regardless of any message to turn off the sector i it mightreceive from some other sectors.

Otherwise, if the rate R is not within the set R0, the scheduler for thei-th sector waits for any request from neighbor sectors who have thesector i in any of their sets Qj(R) for any neighbor sector j and any R.If there is no such request, the i-the sector schedules the packet forthe user.

Although FIG. 4 implies that the control of the sectors by the sectorcontrol arrangements and the sector controllers must occur locally tothe BS, the control of sectors can also be handled globally as amongdifferent cells and sectors in different cells. Global coordinationrequires a fast means of communication among BS's, which is not alwayspossible. Local coordination is usually feasible because all decisionsare local to a BS.

As another simple example, the fixed reuse pattern example with thereuse factor of three can be modified to produce an adaptive pattern.Assume it is time for sector A to transmit while the other two sectorsin the cell are forced to remain silent. Instead of turning off all theother sectors, we may want to allow some of these sectors to transmit attimes when the transmission rate in sector A is higher than a threshold,provided that the requested transmission rates of other sectors are alsohigher than some other thresholds.

Other implementations are within the scope of the following claims. Forexample, the transmission power in some sectors might be reduced ratherthan being shut off completely in a celluar system where thetransmission power can be controlled.

1. A method comprising: at a mobile station, attempting to decode anencoded data packet after each of one or more time slots in which theencoded data packet has been transmitted to the mobile station in afirst sector of a cell of a communication system; during one or more ofthe time slots in which the data packet has been transmitted to themobile station in the first sector, reducing transmission power in asecond sector of the cell from a first power level to a second powerlevel; when the decoding of the data packet is successful, transmittingby the mobile station of an acknowledgment; and in response to theacknowledgement, ceasing transmission of the data packet in the firstsector and restoring transmission power in the second sector of the cellto the first power level in subsequent time slots.
 2. The method ofclaim 1 wherein the transmission of the data packet in the first sectorand the level of the transmission power in the second sector iscontrolled according to a pattern.
 3. The method of claim 2 wherein thepattern is organized in a sequence of time slots and the pattern defineswhich sectors transmit data packets and which sectors reducetransmission power in each of the time slots.
 4. The method of claim 2wherein the pattern is a predetermined pattern repeated over time. 5.The method of claim 2 further comprising: determining a current state oftransmissions in each of the sectors; and determining the pattern basedon the determined current state of transmissions.
 6. The method of claim5 wherein the state of transmissions includes information about ascheduling status of transmissions in neighboring sectors.
 7. The methodof claim 6 wherein the state of transmissions includes information aboutcurrent transmission rates of a sector.
 8. The method of claim 5 whereinthe state of transmissions includes information about a next time slotscheduled for transmission in a sector.
 9. The method of claim 5 whereinthe state of transmissions includes information about a forward linksignal-to-interference ratio measured at a mobile station located withina sector.
 10. The method of claim 5 wherein the state of transmissionsincludes information about an estimated location of a user scheduled toreceive a data packet in a sector.
 11. The method of claim 5 wherein thestate of transmissions includes a fairness parameter for a userscheduled to receive a data packet in a sector.
 12. The method of claim5 wherein the state of transmissions includes information about anapplication type of a user scheduled to receive data packets in asector.
 13. The method of claim 5 wherein the state of transmissionsincludes information about a quality of service level of a userscheduled to receive data packets in a sector.
 14. The method of claim 1further comprising: arranging a frequency reuse factor of one or higherin the communication system.
 15. The method of claim 1 wherein thesecond sector does not transmit any data packets while its transmissionpower is reduced.
 16. The method of claim 1 wherein the second sectortransmits data packets at a reduced transmission rate while itstransmission power is reduced.
 17. The method of claim 1 whereinreducing transmission in a second sector comprises suppressingtransmission in the second sector.